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International Heat Transfer Conference 10

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

UNIFYING THE CONTROLLING MECHANISMS FOR THE CRITICAL HEAT FLUX AND QUENCHING: THE ABILITY OF LIQUID TO CONTACT THE HOT SURFACE

Cetin Unal
Los Alamos National Laboratory Nuclear Engineering and Technology Division Engineering and Safety Analysis Group Los Alamos, NM 87545

Pratap Sadasivan
Los Alamos National Laboratory Nuclear Engineering and Technology Division Engineering and Safety Analysis Group Los Alamos, NM 87545

Ralph A. Nelson
Applied Physics Division, Los Alamos National Laboratory, P.O. Box 1663, MS F661, Los Alamos, New Mexico 87545, USA

DOI: 10.1615/IHTC10.4760
pages 171-176

Abstract

According to previously proposed hypothesis, CHF for power-controlled systems occurs when some portion of the heater surface dries and a local point within this dry patch reaches a critical rewetting temperature, beyond which liquid can no longer contact that point. In this paper, our objective is to examine the validly of the hypothesis when patch characteristics-the shape and number-are varied.
The study revealed the effect of the noncircular shape of the dry patch to be negligible. In the case of a single dry patch, the location of the patch on the heater surface had also a negligible effect. The spatial distribution of multiple dry patches on the heater surface had no sufficient effect. The number of patches, however, did have an effect. Its effect was found to be of the same order as that of the initial thickness reported in the previous study (Unal et al. 1992).
Thus, the results reveal that the predominant influences are the initial macrolayer thickness and the number of patches. An accurate treatment of the dry-patch behavior and its role in the mechanism of CHF must include appropriate consideration of the spatial variation in the macrolayer thickness over the heater surface.

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